Various processes have been proposed for producing hydrogen from water, many of which create oxygen as a by-product. In particular, totally thermochemical H.sub.2 production processes which have the capability to create large amounts of hydrogen have the potential for alleviating problems in the chemical-fuel energy sector (i.e., oil, natural gas, etc.) because they utilize clean sources of heat energy, such as that developed by high temperature nuclear reactors, fusion reactors and concentrating solar collectors. In addition to using the H.sub.2 so formed to create power, it can also be used as a chemical feedstock, for example in the manufacture of fertilizer.
One such "water-splitting" process produces hydrogen iodide as a part of a closed-cycle chain of reactions and is disclosed in U.S. Pat. No. 4,089,940, issued May 16, 1978 to John H. Norman et al. This process is based upon the Bunsen equation whereby sulfur dioxide, water and iodine are reacted to produce sulfuric acid and hydrogen iodide. The hydrogen iodide is separated from the reaction mixture and eventually decomposed in order to recover gaseous hydrogen.